childbearing age than would be present in the stable condition at 1960 age-specific rates of birth and death. This is a well-known result of the low births of the 1930's.
From the age-intrinsic rate to the age-nuptiality intrinsic rate (from 20.8 to 18.4) we find a decline; that means that the proportion of married women in the observed population of 1960 was greater (in the main ages of child-bearing) than the proportion of married women in the stable condition. If the marriage rates, the age-specific nuptial fertility rates, and the age-specific mortality rates of 1960 are allowed to work themselves out, they would result in a lower overall birth rate than would the age-specific fertility and mortality rates of 1960 disregarding marriage.
Demographers find useful information not only in age and marriage but also in birth order. Registrations customarily record whether a birth is the first, second, third, . . . birth to that mother. With complementary information on the number of mothers in the population who have had one, two, three, . .. children we can work out rates of childbearing for women who have had one, two, three, . . . children. Such rates are called parity-specific. The most useful form of calculation does not abandon the previous classes, but works out rates for the several parities for each age of married woman. These are called age-nuptiality-parity rates, or A-N-P for short.
When we go from the age-intrinsic rate to the age-parity intrinsic rate, we find an increase from 20.8 to 23. This can only mean that within each age group the distribution of actual parities is unfavorable to reproduction, and the age-parity intrinsic rate corrects for this. The highest-bearing women are those who have had at most two children, that is, are of parity zero, one and two; apparently the stable condition on 1960 age-parity specific rates would contain relatively more individuals of up to second parity than the observed situation of 1960.
The simultaneous correction for parity and nuptiality brings the rate down. Separation of the married women in the age-parity analysis has so drastic an effect that we find A-N-P below the simple age-intrinsic rateA In short, the effect of nuptiality more than offsets the effect of simple parity. Whelpton (8) did the basic work on parity, and Karmel (9) suggested the importance of nuptiality. Oechsli's (7) recent calculations show the importance of both.
The lozenge form of the diagram may help us follow the preceding arguments.